Radio transmission and reception



Dec. 7, 1937.v

H. B. BREEDLOVE RADIO TRANSMISSION AND RECEPTION Filed Sept. 25, 1935 lim y/mc' haz.

3 Sheets-Sheet 1 Dec. 7, 1937. B BREEDLOVE 2,101,529

RADIO TRANSMISSION AND RECEPTION Filed Sept. 25, 1955 7a mvfa//rfdmsas a,

72 7# 76 7a gm@ 3 Sheets-Sheet 2 Y /57 :.n, ,4a/.1.5- la7 nia/a A' HMH/HEM Dea 7, 1937. H. B. BREEDLOVE 2,101,529

RADIO TRANSMISSION AND RECEPTION Patented Dec. '7, 1937 PATENT QFFICE RADXO- TRANSMISSION AND RECEPTIGN Harry B: Brecdleve,` Memphis, Tenn.V

Application lSeptember 25, 1935, Serial Nc. ,41,986

11 Ciaims.

This invention relates to means and methods for removing or suppressing interference, include ing static, which interferes with'they reception of signa-lling` currents transmitted at radio fre# quencies, either over wire, air or other none metallic. circuits. removal of such, interference inv complete wire circuits, wireand non-metallic return circuits, or radio broadcasting and receiving circuits.

t primarily relates to ymeans and methods for utilizing two of the usualbands of frequencies which bands preferably are adjacent bands, for transmitting and receiving signals at radio frequencies, the interference on one band being used to suppress the interference on the other thereof.

It further relates to means and methods for utilizing two of the usual bands of frequencies for receiving signals at radio frequency, one of such bands being unused, at least locally, so far as 20 transmitting is concerned, or modulated in such a manner that its signal may be ltered out, the

interference on one band being used'to suppress the interference on the other band.

It further relates to means andmethods for 25 utilizing a plurality of bands lof frequencies for receiving signals at radio frequency, one of vwhich bands is left unused at least locally, so far as sending is concerned, or is modulated in such manner that its signal may be filtered out, the interference on such unused band being used to suppress vthe interference on each of the other bands.

It further relates to the Vutilization of two bands of frequencies, which preferably are adjacent bands, and to means and methods for concurrently transmitting a signalling current at radio frequency over such bands, the transmission bands being energized at their respective frequencies and being jointly intensity-modulated out-of- 4 phase, and in receiving these out-of-phase currents, so combining them that tne signalling currents of one' band supplement the opposite-phase signalling currents of the other thereof, while unwanted interference currents that may enter the receiver on one band will oppose and cancel out the inherently in-phase interference currents that enter on the other band.

It is further directed in receiving signalling currents at radio frequency, toward the utilization of two bands of frequencies, one of which bands may be locally-vacant'only and in so combining the currents that unwanted interference current intensity which may enter the receiver on one band will oppose and suppress the inherently iii-'phase interference current intensity on the It'relates to the suppression or.

(Cl. Z50- lill other band,` whereas the signalling current intensity ofthe used band will be opposed by nosignalling current intensity in the signal vacant band.

In usual transmission at radio frequencyv a carrier Awave of desired frequency, intensity modulated, is` suitably amplified,- and is transmittedY from the sending antenna, such carrier waves when received being often accompanied by staticor other interference which'hinders, or even prevents reception.

In the preferred form of my device two such carrier waves, preferably rthough not necessarily, of adjacent'frequencies are jointly but inverselyl intensitymodulated, so that one wave ispr'ef-e'rably at its maximum intensity at the same time the other is at its mini-mum intensity. The twoI waves suitablyamplified, are sent out over a Vjoint antenna or two separate antennae, the Itwo waves so Asent out, asis inherently true of all radioI frequency waves, not combiningftheir frequencies or their-intensities.

The two wavesfso sent 'out are picked up, still in inverse phase in intensity, by a single antenna, or by two antennae -ofthe receiving instrument. If picked up by "a single antenna they may both be jointly tuned; amplified, detected, or converted," and if desired,l beat with a signalfrom a local tuned oscillator, and the two frequencies received, or produced, as the case'may be, separately passed through desired amplifying :stages to detectors wherein they areeach changed into audiofre; quency currents. AThese, inverted vaudio frequency currents are then so combined in the primary of a transformer `that the `two out-of-phase intenq sities supplement each other, and "jointly linduce a current vwhich is amplified and sent out over theV speaker. At the same time interference currents may enter the receiver with both-of these currents, and passtherethrough in the same manner, the intensitieso-f'such interference however being inherently in-phase, so that vthe two intensity phases op-pose each other and the interference is cancelled out or atleast-to a major extent sup` pressed.

Or the two waves whether received by a single antenna or two antennae may be separately tuned," amplied, converted, heterodyned if desired, and passed to and through detectors, the output of these detectors being combined as before; i

In reception also it is possible toy receive a carf particular receiving instrument is concerned is signal-vacant; that is, does not bring into the instrument a signal but which inherently does bring in interference in the same manner as does the signal bearing current.

In reception therefore, the invention makes use of two channels at different frequencies, which channels may be adjacent frequency bands, or separated frequency bands, both channels may have signal energy impressed thereon, which energy has been modulated in intensity in outof-phase relation; or one channel may be signalvacant, and the other thereof signal-bearing, and intensity modulated. In the latter case the signal-vacant channel may be signal-vacant locally only. In either case the receiving apparatus is adapted to receive and be tuned, independently if necessary, to the two channels then being used. Interference, if existent, having its own carrier waves enters the receiving apparatus substantially equal on both the signal-vacant channel and the signal bearing channel. The intensities of the two signal frequencies are then combined in reinverted phase relation, so that the two signal intensities are now supplemental or the single signal intensity is unoppcsed and the signal comes in in full Value, while the interference intensities of the channels oppose and cancel out, one the other.

While a locally signal-vacant channel may be used, a channel left vacant b-y all stations in sending is preferred, and where this is done one signalvacant channel may be used with a number of signal-using or transmitting channels.

It is preferable in reception that the two channels, both signal carrying, or one signal carrying and one vacant, be adjacent. In the standard (long wave) broadcast band this is probably now not possible and such locally signal-vacant channel as may be available must be found and used. In the next higher bands of frequencies however cleared channels may probably be available, though it may be necessary to have one such cleared channel for a number of sending stations, but in the high frequency or short wave bands it appears feasible to clear for each sending station two adjacent bands one of which may be used or left unused as may appear advisable to such station.

The objects of the present invention are:

To provide means and methods of suppressing interference including static in the reception of signalling energy at radio frequency, either over wire, the air, or other circuits.

To provide means and methods for so transmitting and receiving signalling energy at radio frequency either over wire, the air or other circuits, that interference, including static may be cancelled out or suppressed.

The means by which the foregoing and other objects are accomplished and the method of their accomplishment may readily be understood from the following specification on reference to the accompanying drawings, in which,-

Fig. l illustrates the general arrangement of one form of the transmitter, using a single antenna.

Fig. 2 an arrangement for superheterodyne reception, using a single antenna, tuner and converter, and

Fig. 3 a specific hookup between the detectors and the audio frequency amplifier and speaker.

Fig. 4 illustrates an arrangement for tuned radio frequency reception, using a single antenna and separate tuned radio frequency stages.

Fig. 5 illustrates an arrangement for heterodyne reception, using independent antennae and separate tuning and heterodyning channels.

Fig. 6 illustrates an arrangement for tuned radio frequency reception using a plurality of antennae each feeding a tuned radio frequency channel.

Fig. '7 illustrates a modified arrangement of transmitter using two antennae.

Fig. 8 is a further modified arrangement of transmitter in more specific detail, also using two antennae; and

Fig. 9 a third modification, also in specific detail, using a single antenna.

Referring now to the drawings in which the various parts are referred to by numerals;

In Figs. l, 2 and 3; IU and II are constant frequency oscillators operating at different frequencies, which impress their energy on radio frequency amplifiers l2 and i3 respectively. Leads I4 and l5, complete through radio frequency transformer primaries l5, l1 and modulator transformer secondary I8,a circuit from one phase side of amplifier I2 to the opposite phase side of amplifier I3. A center tap I9 and leads 2D, 2l complete the circuits to the amplifiers. v22 is a modulation amplifier connected to the primary 23 of the modulation transformer and which feeds the modulation system. The secondaries 24, 25 of the radio frequency transformers are connected to radio frequency amplifiers 29 and 3U respectively, and the signals of said amplifiers are impressed upon a conventional antenna system 33, 34 and 35 by coils 3l and 32.

The receiver includes a conventional antenna system 4U, 4l, a tuned radio frequency amplifier 42, the output of which is connected to a first detector or converter 43, and there mixed with local tuned oscillator signals from an oscillator 44. Output of detector 43 is connected to two intermediate frequency amplifiers 45 and 46, which are tuned to frequencies having the same differences as that between the oscillators l0 and i l. The outputs of amplifiers 45 and 45 are further amplied by intermediate frequency amplifiers 41 and 48 respectively, and the outputs of these latter amplifiers are fed into second detectors 49 and 50 respectively.

The outputs of detectors 49 and 50 are connected to the opposite ends of the primary 5I of a transformer. The center of this primary is connected back to both detectors. The secondary 52 ofthe transformer is connected to amplifier 53 and the output of this amplifier is impressed on speaker 54.

Fig. 3 shows a specific hook-up between the detectors 49 and 50 and the amplifier 53. In this modification the output of detector 49 is connected through a push pull transformer 55 to the grids of electron discharge devices 5, 5l, and the detector 58 is connected in inverse phase relation through push pull transformer 58 to the grids of electron discharge devices 5S and 6E). The plates of electron discharge devices 56 and 59 are Vconnected to one side of primary 5i of a third transformer, and the plates of electron discharge devices 51 and 60 are connected respectively to the opposite sides of the primary 5l of the third transformer. pull transformers and primary of third transformer are tapped and connected back to heating elements or cathodes, of the electron discharge devices.

In this type of the device shown in Fig. l two Secondaries of the push carrier Wavesunmodulated are-generated vof dif-Y ferent frequencies byoscillators' |0 and Y| and passed separately in usual manner througlifampliers |2'and v| 3,.v to the primaries I8 and Hiof transformers in` which they'aremodulated, inverselyasltoin-tensity, by modulation'tra'nsformcr |8-23. The modulated waves from secondaries 24S and 215; of the transformers are impressed on amplifiers 29 and 39 respectively,Y and placed on the-antenna system, 33, 34iand 35, thereby being transmitted.

The waves thus sent out are picked up still in inverse intensityby antenna1system'40, 4| tuned and ampliedby amplifier-tuner 42,` impressed upon converter 43, and beat with signal from a local tuned oscillator 44. The beat frequencies caused by the difference of the incoming signals and the localoscillator produce through these converters two frequencies-or heterodynes, the difference of lwhich frequencies is equivalent to the difference in frequency of the two transmitted waves. 'I'hese two heterodyne signals are amplified and tunedV through separate channels 45-41 and i6-48 toy second detectors 49 and-50, the signals remaining of inverse intensity. Outputs of detectors 49, 50 pass through primary 5| of the transformer, thereby creating the usual maximum inductance in secondary 52, andithence to amplifier 53 and speaker 54.

During the cycle thus described, static or other interference which may be -received and amplied is carried by both of the channels-at substantially equal intensity, this intensity on both channels being in phase and being receivedwith the incoming signals one of which is of opposite phase. Interference passes with such signals to the transformer l-52, but being of the same phase, the phases are opposed ini the primary 5| and thereby induce a minimum, if any current in secondary 52, and for practical purposes are eliminated, whereas the vout-of-phase signal currents,` supplement one the other and create maximum induction.

In the modificationl shown in Fig. 3 the output of the detector 49 passes to the push pull transformer'55 and from the transformer 55 to the electron discharge devices 56 and 512y The inter: ference current vand the signal current relatively out-of-phase pass from the detector 50 to the push pull transformer 58and thence to the electron discharge devices 59ian'd 69.- From the electron discharge devices k5|5--59 and-51-60'the current flows to the primary of the transformer 5|52; the interference currents being in-phase oppose each other and create a minimum current flow; whereas the signal currentsbeing of opposite phases create a maximum current flow in the primary 5|, and these Vflows induce corre-` sponding currents in the secondary 52, .the interference currents being for practical purposes eliminated and the signal currents carried through at a maximum intensity to the amplifier 53 and the speaker 54.

In Fig. 4 a tuned radio frequency receiving system is shown which uses a single receiving antenna 10, 1| and two tuning amplifying channels employing tuner-amplifiers 12-14--16 and 13-4 -11 respectively, and detectors 18, 19, the output from the detectors passing through transformers 80, 8 I, the secondaries 82, 830i the trans formers being inter-connected in inverted phase relation andy jointly leading to an audi'oifrequenc'y amplifier 84 and speaker 85.

In Fig. 5 a receiving system of super-heterodyne type is shown in which two frequencies are received-over independent! antennae and sepa-y ratelytunediiand.am-plied.' 90, 9| respectively are the antennae systems 92, 93 radio frequency tun'ereamplifiersin which radio frequency' cur; rents are' takenfromthe antennae systems tuned and vamplifiedindependently.v 94, 95 are local oscillators `which are tuned independently and 95," 51 converters. 9B'-99, |00|0| are tuned intermediate frequency amplifiers and |02, |03 are detectors.v Detectors |02 and |93 are connectedfby'leadsHM, |05 through condensers |06, |01y to oppositerends'of the primary |08 of a transformer. A- center tap |09 connects the primary |581 through joint return leads H0, to the-opposite sides of the detectors |02, |93 respectively; Leads |04, |05 are bridged by a resistance! 2', fromawhich a variable tap |3 is also lead to the joint return circuits l0, ||4 is the secondary of the transformer, 5 an audio frequencyvampliiierand H6 the speaker.

Fig. 6 is a receiving system of the tuned radio frequency'type using a plurality of antennae and a plurality of channels, one of the channels being vacant insofar as sending is concerned. is a conventional tuner-amplifier Which may be independently tuned to the ydesired frequency of a transmitting station. |2| is a similar tuner-amplier, which may be tuned to the frequency of a second transmitting station and |23 is a furthersimilar tuner-amplifier which may be tuned to the frequency of a' signal-vacant channel, such channel being either a fully cleared or at least locally-Vacant one. |24, and |26 are detectors for the respective channels. l |21 and |28 are respectively audio frequency amplifiers connected respectively `to the'output of detectors |24y and |25; andl |23, |30 are similar audio frequency ampliers connected to the output of detector |25. The outputs of amplifiers |21 and |29 are connected vto opposite ends of a variable resistor isi and alsothe'condensers |4|V|42 to the opposite ends of the primary |32 of a transformer.` Similarly the outputs of amplifiers |28 and |31) are connected to the opposite endsY of a variable resistor |33`-and also through condensers |43- |44 to the opposite ends of the .primary |34 of the transformer, these connections and the remaining connections being similar to those shown in Fig. 5; |35, |36 being the secondaries respectively of the two transformers. frequency'arnplifiers and |39, |40 speakers.

In Fig. 7 a modification is shown in which |50, are constant frequency oscillators operating at different frequencies, which impress their energy on radio frequency amplifiers |52, |53 respectively.

The outputs of these amplifiers is connected to transformers |58 and |51 respectively then to opposite ends of the secondary |58 of a modulation transformer, the center tap |59 of this transformer being connected back to amplifiers |52 and |53, and the primary |69 being connected to a incdulationamplier |54. The secondary of transformer-|56 is connected to an antenna sysle'L' |62' and the' secondary vof transformer lfrto anantenna system |53, |64. `represents the ysource of the modulation energy of amplifier |54.

Fig. 8 is a schematic drawing showing the hookup of a transmitter employing two antennae. |10 and |1| are variable condensers. |12 and |13 are tapped coils. |14 and |15 are resistances. |16 and|11 are electron discharge devices. |18 and |19 are variable condensers. |80 and |8| are coils. The parts |10, |12, |14, |16, |18,

|31, |38 are audio ing a second radio frequency amplier.

constitute one tuned oscillator and the parts, |1|, |13, |15, |11, |19 and |8| a similar tuned oscillator. |82 and |83 are sources of electrical energy which operate the two oscillators jointly.

|84 and |85 are radio frequency chokes. |86 and |81 are variable condensers. |88 and |89 are electron discharge devices. |90 and |9| are variable condensers. |92 and |93 are the primaries of radio frequency transformers. |94, |95, |96 are sources of electrical energy which operate these parts jointly. The parts |84, |86, |88, |90 and |92 form one radio frequency amplifier and the parts |85, |81, |89, |9| and |93 a similar radio frequency amplifier. The two amplifiers just described are connected to opposite ends of the secondary |91 of a modulating transformer, the center of which secondary is connected to the source of electrical energy |96. The primary |98 of the modulation transformer is connected to a source of modulation energy (not shown), by leads |99. The secondaries 200, 20| of the radio frequency transformers are connected to conventional antenna systems 202, 203 and 204, 205 respectively, being tuned by variable condensers 206, 201.

Fig. 9 is a schematic diagram of a transmitter using a single antenna system, and also using crystals in the oscillator circuits. In ythese circuits 220 and 22| represent crystals. 222 and 223 are resistors which bridge the leads from these crystals, 224 and 225 are electron discharge devices. 226 and 221 are respectively the primaries and 228, 229 the secondaries of two radio frequency transformers, the primaries 226 and 221 being respectively tuned by variable condensers 230, 23|. The parts 220, 222, 224, 22S and 230 form one fixed frequency oscillator, and the parts 22 223, 225, 221 and 23| form a similar fixed frequency oscillator. The two oscillators being adapted to operate at different frequencies. 232 and 233 are the primary and secondary respectively of a modulation transformer, and 234 and 235 are sources of electrical energy which energize the two oscillators. The primaries 226, 221 of the radio frequency transformers are connected to opposite ends of the secondary 233 of the modulation transformer.

236, 231; 238, 239; and 242 and 243 are variable condensers and 240, 24| are electron discharge devices. 244, 245 are coils. The secondary 228 has its leads bridged through the variable condenser 236, the electron discharge device 240 is neutralized by the condenser 238, and the coil 244 with its leads is bridged through the variable condenser 242, these parts forming one radio frequency amplifier; and the similar secondary 229, electron discharge device 24| and coil 245 with their connecting leads are similarly bridged and neutralized by condensers 231, 239 and 243, form- These two amplifiers are coupled by joint leads 246 and 241 tapped into and leading respectively from the coils 244, 245, and through the energy sources 249, 250 and 25| which operate the two ampliers. 256 is a microphone or other source of modulation energy. 251 is a coupling transformer and 258 an electron discharge device which is connected to the primary 232 of the modulation transformer. 252 is a coil which is inductively coupled to the coils 244 and 245. 253 and 255 are an antenna system bridged by a variable condenser 254.

It will be distinctly understood that tuned radio frequency receivers such as are indicated in Figs. 4 and 6 or superheterodyne receivers such as are shown in Figs. 2 and 5, may be used interchangeably in all of the modifications.

It will also be understood that the receiver systems in the main may consist of two standard tuning amplifying and detecting systems inversely connected and delivering to a single speaker.

It will also be understood that variably tapped resistance bridges similar to the resistance bridges ||2, of Fig. 5 and the resistance bridges |3| or |33 of Fig. 6 may be introduced in the forms of receivers shown in Figs. 2 and 4 should it be so desired.

Operation, transmission In transmitting, using any of the transmitter forms shown, two carrier waves suitably energized as by the energy sources |82, |83 of Fig. 8 or the energy sources 234, 235 of Fig. 9 are passed through the two oscillators and two differing desired frequencies determined in the waves by the two oscillators. Should it be feasible these two frequencies are adjacent frequencies so spaced that when properly modulated in intensity the intensity swings do not overlap. In other words the two frequencies respectively lie each in a transmission band such as is established and allotted under present conditions to a sending station. While these frequencies are preferably adjacent they may be separated, that is, have other frequency bands intervening. The two carrier waves thus established are then separately amplified in usual manner as in the amplifiers I2, I3 of Fig. l; |52, |53 of Fig. "I; or the amplifiers of Fig. 8, and are jointly modulated inversely in intensity by energy from the modulation amplifiers 22 of Fig. 1; |54 of Fig. '7; or from the modulator not shown brought in through the leads |99 of Fig. 8, this inversion of intensity being accomplished by reason of the opposite connection of the secondary |8 of the modulation transformer to the primaries I8 and |1 of the radio frequency transformers, Fig. 1; the similar connection of the radio frequency transformers |56, |51 of Fig. 7, through the secondary |58 of the modulation transformer in Fig. 1; or the like connection of the primaries |92, |93 of the radio frequency transformers through the secondary |91 of the modulation transformer in Fig. 8; and after such intensity inversion, the intensity frequencies set up in the secondary of these radio frequency transformers as intensity modulated are sent out over the antenna system which may be either a single antenna or two antennae as may be desired.

In Fig. l radio frequency amplifiers are introduced between the radio frequency secondaries and the antenna system and these may be similarly introduced in the form shown in Figs. 7 and 8 though they have not been so shown.

In Fig. 9 the same essential steps are followed, except that the frequency waves are not amplified before being modulated in intensity but are amplified after such modulation and before placing on the antenna system.

Transmission for any of the forms of reception herewith may also be accomplished by any standard intensity modulated transmission system of the present type provided only there be a signalvacant channel available at the receiving end. In furtherance of this, a transmitting station having two channels available for transmission may make use of one only thereof, leaving the second channel signal-vacant, and in such case, additional transmitting stations may avail themselves of the same signal-vacant channel, such signal-vacant channel being available for use in reception fromany onefof suchstationsv Itf'is preferable that the two channels'nsed be adjacent. An extremely desirable condition in such case would be''a vacantchannel lying adjacent to and between" two signal-used channels whereby each signal-Used channel willA have 'an adjacent signal-vacant channel. In such case also the signal-vacant channel would also be available for other signal-using channels. In the absence of a channelsignalLvacantthroughout, a channel locallysignal-vacant may also be used.

Operation, reception In reception two carrier waves of differing frequency, jointly modulated in inverse intensity by one signal modulator may'be'received over a single antenna as shown in Figs. 2 and 4 or over separate antennae as shown in Figs. 5 and 6.

In Fig. 2, two 'radiofrequency carried waves, modulated inversely in intensity, received over the antenna'syst'em 40, 4|, are broadly tuned by radio'frequency vamplifier tuner 42 andY passed to a converterorfirst detector 43, and there beat with a signal froml a local tuned oscillator 44, the output of the converter being separated' and passedVv in parallel Vthrough intermediate frequency amplifiers 45,4%; 41, 48 to detectors 49, 56 respectively, each frequer'icyy bei-'ng in these channels ampliied, tuned, ltered-anddetectedinthe usualmanner. The audiofrequency currents' set up in the detectors arestill-in out-of-phase intensities as theyweresent out from the transmitter and due to thein'verted lhookup of the detectors "49," 50 arel re-invert'ed into complementary phase relation in the primary 5|, inducing a current whichis amplified and sent out throughthefs'peaker'll. If static orA interference exists, having'itsown-"carrier waves, it is received on the antenna system and is broadly tuned by the tuner amplifier 42,; those frequency currents correspondingtothe frequency of the signal carrying waves being passed to the converter -and beat with thel signal from the'local tuned oscillator. The 'lmixed outputs from the converter separate and pass inthe same manneras the signal carrying currents in parallel, through the two sets of intermediate-frequency amplifiers, to the detectors 49, 50 wherein they also are changed into audio frequency currents. These interference currents however having been received on the antenna: inherently in in-phase intensities, the intensities of the interference audio frequency outputs of the detectors, are also in-phase and entering opposite ends of the transformer primary 5| therefore oppose each other, cancelling the one the other out so that substantially none of the interference intensities are available to interfere with the signal output of the speaker.

In Fig. 4 substantially the same action accurs except that the two intensity inverted `signalling frequencies, each accompanied by-an interference frequency, are individually tuned, amplified and detected, the detector outputs being' combined as before and Apassed to the speaker; and the same condition occurs in the form shown in Fig. 5 with the exception that reception is over two antennae instead of over one antenna.

In Fig. 5 however (and also in Fig. 6), the outputs from the detectors |02, |03 passing to the primary |08 may be balanced either in so far as the signalling frequencies are concerned, or in so far as the interference is concerned by adjusting the tap H3 relatively to the resistance bridge I2. Particularly therefore where the frequencychannels are not adjacent and the interference intensities are'unequal, it vis possible by shifting the relation of the tap and the bridge, to so balance the interference that the two opposing phases are equal and actually balance out. This shift may unbalance the signalling currents but since such currents are supplemental, in no way affects' clear reception of such currents.

The form shown in Fig; 6 is only usable with a cleared or'locally vacant channel and with single channel transmission. In this form, intensity modulated signalling waves from one stationand interference waves are received, tuned anddetected through tuneramplier |20, and detector IM; and from lthe same or another station through tuner-amplifier |2|, and detector |25, and the detectedoutputs delivered through' ampliers |21, |28 'respectivelyto the primaries |32, |34. Interference waves'unaccon'ipanied by signalling waves `are received tuned and detected iby, tuner-amplifier |23 Vand detector '|`2|,"`and the detectoroutput delivered parallel'tl'irough amplifiers |29, |30 `to the opposite Vends of: thetwo primaries |32,I34 respectively, this interference being balancedA by the". variably tapped brifdg'es |3|,'|33, in the'.respectiveprirnaries,fand2 can-A celling Vout the "opposedphase interference such primaries, leaving the signalling currentsrto pass unopposed and induce current'in theirf'respective secondaries," whichY 'are amplified and sent outthrou'gl'iv the'spealiers. It will 'be understood that while ytwoV signal-wave receivers'l only are' shown, theseare merely'typicalof a plurality of such receivers, all of Vwhi'chf may be interference cleared by a single 'signalvacant receiver.

In any of the forms of thefdevica: including Fig. 6, signalling currents may be'rec'eivedffrom a transmission systemof usual type sendingout the usualfsi'ngleband of intensity modulated signal carrierwaves. -In su'chca'se,V4 as'for example, inFig. 2, the signal carrier wave accompanied by aninterferenc'e carrier wave of like frequency received over the antenna, leaves'ithe tunerlanvplifier 42 and a second interference carrier Wave of? different frequencyun'accompaned by afs'ignal current, also leaves such tuner and areallA 'detected'and beat with the 'signal from the local tuned oscillatorM and the outputsV passed in parallel' through the intermediate-frequency ampliers:45441,l`and`46448 to thedetectors 49 and5|l` respectively, 'the output'of one detector carrying interferenceandsignal, andv the output of theotherdetector 'carrying interference only. The outputs of these two detectors then combine in inverted'relation, in the' primary 5| of the transformer, the two interference current intensities opposing andcancelling one the other, and the'signal intensity'being'unopposed passing to the speaker.

It will be understood'that 'the amplifiers |21, |28, |29fand |30, shownv in Fi'g.'6'prevent feed back from the coils |32, and' |34 through the circuits that lead thereto from the several detectors |24, |25 'and |26,'and'thereby prevent interference between'programs received over the various circuits.

What I claim is: I 4

l( In a receiver for intensity modulated 'radio frequency currents and which employs tuning andY amplifyingmeans, dual detectors, 'each having an output transformer, twopai'rs kof electron discharge'devices, a third transformerghaving' its primary inverted with relation'tothe primary Aof one said output transformerjjaridan'amplifier and speaker connected to the secondary `"of "said third transformer; 'means connecting. opposite ends of the secondary of a rst said output transformer respectively each to the grid of a rst said electron discharge device of each said pair of said devices, means connecting opposite ends of the secondary of the second said output transformer respectively each to the grid of the second said electron discharge devices of each said pair of said devices, means connecting both plates of a rst said pair of said devices and both plates of the second said pair of said devices respectively to opposite ends of the primary of said third transformer, interconnected taps connecting the secondaries of both said output transformers to the cathodes of said electron devices, and a tap connecting the primary of said third transformer to said cathodes.

2. In a receiver for intensity modulated radio frequency currents and which employs tuning and amplifying means, dual detectors, each having an output transformer, electron discharge means in duplicate, each means having a pair of grids and a plate, a third transformer, having its primary inverted with relation to the primary of one said output` transformer; and an amplifier and speaker connected to the secondary of said third transformer; means connecting opposite ends of the secondary of a first said output transformer respectively to a first grid of a firstv said electron discharge means, and a rst grid of the second electron discharge means, means connecting opposite ends of the secondary of the second said output transformer respectively to the second grid of said rst electron discharge means, and the second grid of said second electron discharge means, means connecting the said plates of said first and second said electron discharge means respectively to opposite ends of the primary of said third transformer, interconnected taps connecting the secondaries of both said output transformers to the cathodes of said electron devices, and a tap connecting the primary of said third transformer to said cathodes.

3. Means for suppressing interference in radio reception, including means for establishing at least three channels, each for tuning and detecting a carrier wave of desired frequency, means for combining the output of one of said channels in out of phase intensity relation severally with the output of each of theV others of said channels respectively, and means for independently delivering the unopposed signal output of each of the latter said channels.

4. Means for suppressing interference in radio reception, including means for establishing at least three channels, each for tuning and detecting Va carrier Wave of desired frequency, means for combining the output of one of said channels in out of phase intensity relation severally with the output of each of the others of said channels respectively, means for preventing feed back from each of said channels to another thereof, and means for independently delivering the unopposed signal output of each of the latter said channels.

5. Means for suppressing interference in radio reception, including means for establishing at least three channels, each for tuning and detecting a carrier wave of desired frequency, means for combining the output of one of said channels in out of phase intensity relation severally with the output of each of the others of said channels respectively, said combining means including means for severally adjusting each said phase relation, and means for independently delivering the unopposed signal output of each of the latter said channels.

6. Means for suppressing interference in receiving Waves at radio frequency, which includes using at least three receiving means, each having means for independently tuning, amplifying and detecting a modulated carrier wave, means for mixing the detected output of one said receiving means severally with the detected outputs of each of the others of said receiving means in phase relation to cause the intensity phase of the interference modulations of the carrier Wave received on the one said receiving means to oppose the intensity phase of the interference modulations of the carrier Waves received on each of the other said receiving means, whereby in each to substantially cancel out said interference; and means for subsequently independently amplifying and delivering the unopposed signal output of each of the latter said receiving means.

7. Means for suppressing interference in receiving Waves at radio frequency, which includes using at least three receiving means each having means for independently tuning, amplifying and detecting a modulated carrier wave, means for mixing the detected output of one said receiving means severally with the detected outputs of each of the others of said receiving means in phase relation to cause the intensity phase of the interference modulations of the carrier wave received on the one said receiving means to oppose the intensity phase of the interference modulations of the carrier Waves received on each of the other said receiving means, means for severally adjusting said phase relations, whereby in each to substantially cancel out said interference; and means for subsequently independently amplifying and delivering the unopposed signal output of each of the latter said receiving means.

8. Means for suppressing interference in receiving Waves at radio frequency, which includes using at least three receiving means, each having means for independently tuning, amplifying and detecting a modulated carrier Wave, several means for mixing the detected output of a rst of said receiving means with the detected outputs of each of the others of said receiving means respectively in phase relation to cause the intensity phase of the interference modulations of the carrier Wave received on the first said receiving means to oppose the intensity phase of the interference modulations of the carrier Waves received on each of the other said receiving means, circuits, leading severally from the detecting means of said first receiving means each to a said mixing means, circuits leading from the said detecting means of said other receiving means each to a said mixing means, and amplifiers, interposed one in each of said circuits.

9. Means for suppressing interference in receiving Waves at radio frequency, which includes using at least three receiving means, each having means for independently tuning, amplifying and detecting a modulatedy carrier wave, several means for mixing the detected output of a rst of said receiving means with the detected outputs of each of the others of said receiving means respectively in phase relation to cause the intensity phase of the interference modulations of the carrier Wave received on the first said receiving means to oppose the intensity phase of the interference modulations of the carrier waves received on each of the other said receiving means, circuits, leading severally from the detecting means of said rst receiving means, each to a said mix.

ing means, circuits leading from the detecting means of said other receiving means each to a said mixing means, and means interposed, one in each said circuit for preventing feed back from its related mixing means therethrough.

10. The method of suppressing interference in receiving waves at radio frequency, which includes tuning, and detecting a carrier wave intensity modulated by unwanted interference free from signal modulation; independently tuning, and detecting a plurality of carrier waves at dif ferent frequencies, each said wave intensitymcdulated by a desired signal and by unwanted interference, and mixing the detected output of said signal free wave severally with the detected outputs of each of the others of saidrwaves in phase relation to cause the intensity phase of the said signal free Wave to oppose the intensity phase of the interference modulations of each of the other thereof, whereby in each to substantially cancel out said interference; and subsequently severally amplifying and delivering the unopposed signal outputs.

11. The method of suppressing interference in receiving Waves at radio frequency, which includes tuning and detecting a carrier wave intensity modulated by unwanted interference free from signal modulation, independently tuning and detecting each of a plurality of carrier waves at different frequencies, each Said wave intensityrnodulated by a desired signal and by unwanted interference, mixing the detected output of said signal free wave severally with the detected outputs of each of the others of said waves in phase relation to cause the intensity phase of the said signal free wave to oppose the intensity phase of the interference modulations of each of the other thereof and severally adjusting said phase relations, whereby in each to substantially cancel out said interference; and subsequently severally amplifying and delivering the unopposed signal outputs.

HARRY B. BREEDLOVE. 

